The scene unfolding yesterday was like one from a movie or a nightmare. A woman taken hostage in the middle of a day by a criminal, claiming to be armed. In situations like this, hostage negotiators are charged with making split second decisions that could mean life or death. Abc's senior justice correspondent pierre thomas takes us inside the high stakes drama, which includes some disturbing immechanicals. Denver, colorado. A tense standoff unfolds. A suspect who claims he's armed takes hostages in this convenience store. The suspect decides to use this woman as a human shield. He wants to escape. The officers said they had to let the hostage go. He refused. With each step, the situation is becoming more dangerous. He attempted to drag the female back in the store. Reporter: Police aren't going to let him get away. The suspect is critically wounded, shot in the shoulder. The hostage is shaken but is not injured. Dangerous hostage situations playing out across the country. Police haven't to make split second decisions with life and death literally hanging in the balance. Watch this frightening standoff at the walmart in midwest city, oklahoma, caught on tape last summer. The suspect takes a baby from its mother's cart while her back is turned he puts a knife to the 2-year-old child's throat. There's a black guy that has a kid, he took this woman's kid. Police try to calm the suspect down. The man starts counting down from 60. The decision is made to shoot. Sometimes the police have more time to make the life and death call. Last year, alabama school bus driver charles poland is killed and a little boy who has autism is snatched by an angry, deranged man, jimmy lee dikes. What's going on? Reporter: To make matters worse, the boy is being held in an underground bunker, complete with booby traps. As police arrive at the scene, they discover he's planted a bomb in this pipe he planned to talk to police through. They were on top of the pipe. He could detonate the bomb at anytime. Reporter: Fbi behavioral scientist is flown down to alabama to help in the unfolding crisis. He was angry, but intelligent and controlled. He coldly made a promise to mr. Poland. You will do this or I will kill you. And he killed him. Jimmy lee dikes is known as mean man because of his anti-government rants. A decorated navy veteran, he was due in court to face charges of shooting at a neighbor. The hostage team, which includes top negotiators quickly tries to soothe dikes in direct tyke talks on the phone. We wanted to try to come in and calm the situation down, calm down his emotions and try to stabilize what is a really volatile situation. Reporter: And they knew he was watching tv in that bunker. So they carefully tailored the message when addressing the cameras. I want to thank him for taking care of our child. Back in the bunker, dikes grows more dlij rabelligerent by the day. By the end of the day, there's going to be a determination just exactly what the hell is going to take place. Reporter: Soon he's suicidal. By day six, the danger to ethan is increasing by every second. He was handling the weapons and the bomb inside the bunker on a more frequent basis. Reporter: The decision is made, they have to try to take ethan out by force. Then comes the moment of truth. I was scared. Knowing what was waiting for them down there, they went anyway. Chilling. Reporter: As the team reaches the bunker with a stun grenade, that detonates the bomb. Smoke begins pouring out of the bunker. The tactical team descends into darkness. Dikes begins shooting. Silence. Dikes is shot and killed in the confrontation. The agents were okay. Remarkably sustained no major injuries. Deadly force has deadly consequences. Actually taking a human life is a big deal. It's not easily done. And they have to be prepared for that. Chris voss is a former fbi hostage negotiator. We asked him to dissect this week's denver standoff. If in his opinion police did the right thing. Based on what they know at the time, if reasonably he has a gun, they have reasonable grounds to believe she's in fear for her life. She's in imminent danger. She's moving in a direction where he might possibly escape with the hostage. Which is the worst of all possible scenarios. Reporter: Voss said matters can get even more dicey when the hostage starts to struggle as she is pushed. The threat level is increasing even more and increases the likelihood that he could either intentionally or accidentally kill her. As he makes his move back into the store, the pressure builds. This is getting more dangerous by the moment. Especially with his refusal to go back inside. Reporter: Police take the shot. Police have yet to reveal whether the suspect actually had a gun or not. But for voss the decision is clear. That was completely appropriate. They had no choice. I don't see any other options here at all. Reporter: No choice, trigger pulled and another standoff is over. It will not be the last. For "nightli" I'm pierre thomas in washington.

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